His comments, while linked to the holy celebration, came as sectarian violence spiked again in Iraq, with the execution-style killings of at least 87 people, including about 29 bodies piled in a mass grave in a Baghdad neighborhood. Hundreds of people have been killed since the Feb. 22 bombing of a Shiite mosque in Samarra, creating concern that the country may be tipping toward civil war.

Rumsfeld said Gen. George Casey, the top U.S. military officer in Iraq, "may decide he wants to bulk up slightly for the pilgrimage."

The holiday, which ends March 20, includes pilgrimages to holy sites in Najaf and Karbala. Increased attacks marked the celebration during 2004 and 2005.

Rumsfeld said the U.S. is continuing to shift responsibilities to Iraqi security forces, but he would not say how long U.S. troops are expected to stay in Iraq.

"Do we think we're going to be there four or five years more in terms of large numbers of U.S. ground forces?" said Rumsfeld. "The answer is no, I don't think so. Those are decisions for the president."

There are about 133,000 U.S. troops in Iraq. Rumsfeld did not specify how many troops might be added.

Rumsfeld and Bush have repeatedly said that conditions in Iraq will determine the number of U.S. troops deployed there.

In other comments, Rumsfeld said it is likely that the government of Iran is backing efforts by members of its Republican Guard to incite violence in Iraq.

While he said it is difficult to draw a direct line to the Iranian government, he said a reasonable man would deduce that members of the guard "are not freelancing" and are not pilgrims traveling to holy sites in Iraq.

Rumsfeld's comments expanded on his recent accusations that the Al Quds Division of Iran's Revolutionary Guard are trying to stir up trouble in Iraq by helping to move explosives and bomb-making material across the border from Iran.

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